Positive non-interfering transmitter

ABSTRACT

A plurality of transmitters utilizing common wiring are connected to a control unit having a power reversal relay. The transmitters each incorporate a diode and a rectifier protected motor that activates a coded signal on a separate signal line. Activation of any one of the transmitters causes a reversal of polarity and shunts the diode therein, thereby allowing operation of the one transmitter while power is blocked from the other transmitters until the complete signal has been transmitted.

[ Apr. l7, 1973 Primary Examiner-Donald J. Yusko AltorneyJ. Gary et al.

[57] ABSTRACT A plurality of transmitters utilizing common wiring areconnected to a control unit having a power reversal relay. Thetransmitters each incorporate a diode and a rectifier protected motorthat activates a coded signal on a separate signal line. Activation ofany one of the transmitters causes a reversal of polarity and shunts thediode therein, thereby allowing operation of the one transmitter whilepower is blocked from the other transmitters until the complete signalhas been transmitted.

8 Claims, 1 Drawing Figure non, Shelby, Ohio Federal Sign and SignalCorporation, Chicago, Ill.

Oct. 19, 1971 ..340/2 l7, 340/295 .G08b 17/06, G08b 25/00 .340/415, 217,295, 340/412, 150, 160

References Cited l/ 1 I ||u|l||||4 I.

M I/ o l n lllllilllL |||u|)|l|||4 Y O AV I n I liiw W a) 4 Il1l l l l l.1 6 1 a w WW? M A 0 m U4 E u .4. mm if TRANSMITTER Inventors: Joe D.Reynolds; Kenneth V. Can- Appl. No.: 190,543

Int. Field of Search....................

UNITED STATES PATENTS United States Patent Reynolds et al.

[ POSITIVE NON-INTERFERING [73] Assignee:

22 Filed:

POSITIVE NON-INTERFERING TRANSMITTER BACKGROUND OF THE INVENTION Thisinvention relates to a system of transmitters utilizing common wiringfor power and for transmitting signals to a common receiver and moreparticularly to a system having means to positively prevent interferencebetween transmitters.

Transmission systems for fire alarms or the like may include a pluralityof separate stations utilizing common wiring and being connected to acommon signal receiver. Transmitter stations utilized in fire alarm orsimilar circuits are normally designed to transmit individualidentifying codes of each station. For this purpose, a code wheel isrotated for three or four revolutions, which in turn closes and opens asignal contact in a sequence unique to the station.

In connection with systems having a plurality of transmitting unitsutilizing common wiring, various types of circuits have been proposed toprevent interference because of simultaneaous or possible overlappingoperation of two or more units. In a series noninterfering or shuntnon-interfering circuit (SNI) having a central control and a pluralityof transmitters, the operation of a first transmitter in the circuitwill be interrupted by the activation of any other transmitter which iselectrically closer to the control than the first transmitter. Since thefailure to receive a signal in such systems may create a dangeroussituation and defeat the essential purpose of the system, it isdesirable to provide a non-interfering system in which the transmittersmay be activated in any order and yet all signals will be received. Suchsystems are commonly described as positive non-interfering systems andinclude some means of effectively preventing interference betweentransmitters that utilize common wiring.

BRIEF SUMMARY OF THE INVENTION The present invention provides forpositive non-interferening operation with the addition of very few partsover that required for a basic SNI system. In accordance with thepresent invention, a blocking diode is incorporated into eachtransmitter such that reversal of polarity of the power source willprevent energization of any transmitter. The control unit includes apower reversal relay that reverses the polarity when any of thetransmitters is activated, thereby cutting off power from the othertransmitters. At the same time, a shunt around the diode of the firstactivated transmitter completes a reverse circuit, which powers a DCmotor through a rectifier, and the motor operates the code wheel, Afterthe appropriate coded message has been transmitted, the polarity isagain reversed, thereby permitting sequential operation ,of any othertransmitters ready for energization.

THE DRAWING The FIGURE is a schematic of the circuit employed in thepractice ofthe presently described invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The circuit of the drawingincludes a power loop having a positive line and a negative line 12, aswell as a separate signal line 14, all being connected to a control unit16. The signal line may be connected to any suitable receiver havingsome form of alarm. A plurality of transmitters, such as 18 and 20 areconnected in parallel in the power loop. The power loopand the signalline 14 may be connected to a conventional end-of-line electronics 22,the purpose of which is to supervise the circuit and detect breaks in orgrounding of the wiring of the power loop and signal line.

It may be seen that the transmitters 18 and 20 are identical, and onlythe transmitter 18 will be described, with identical corresponding partsin the other transmitter being denoted by the suffix a." Thus, eachtransmitter comprises starting contacts 24, which are intended to bemanually or automatically closed to initiate a signal. The contacts 24,could, for example, comprise a manually operated switch on a fire alarmbox and are of the type which will lock in a closed position until thesignal has been completed or until manually reopened.

One side of the starting contacts 24 is connected to the positive line10 through the cathode of a diode 26, which renders the transmittercircuit unilaterally conductive from the positive side or line 10 to thenegative side or line 12. A shunt 28 having normally open contacts 30 isprovided around the diode 26 to bipass the diode when said contacts areclosed. The other side of the starting contacts 24 is connected througha rectifier 32 to the negative line 12. The rectifier preferablycomprises four diodes connected together in a box configuration andhaving diagonally opposite leads connected to a DC motor 34, with theother leads of the box connected to the respective contacts 24 andnegative line 12. The diodes of the rectifier 32 are arranged to assurethe same direction of current flow through the motor irrespective ofdirection of current flow through the transmitter. Thus, the motor isconnected between two anodes on one side and two cathodes on the otherside.

Normally closed series contacts 36 are associated with each transmitter18 and 20 on the positive line 10, and when closed, complete the circuitbetween the transmitters and the control unit 16, which provides therequired power for the circuit. A coding contact 38 associated with eachtransmitter is connected in parallel between the negative line 12 andthe signal line 14, the purpose of which is to complete the signalcircuit under conditions as will be hereinafter fully explained.

The motor 34 of each transmitter is operative, upon energization, torotate and to sequentially close the shunt contacts 30 and open theseries contacts 36 and then to close the signal contacts 38, andthereafter to close and open the signal contacts in a predetermined orcoded sequence. The control unit 16 includes a power reversal-relay 40connected in the power loop, which serves to reverse the polarity ofpower through said loop upon receipt of a single signal pulse from anyof the transmitters.

Having thus described the components of the circuit, the functionthereof will now be described. Initially, none of the transmitters 18 or20 has been started, and current flows around the loop from the positiveline 10 to the negative line. Assuming first that the contact 24 isclosed in transmitter 18, unidirectional flow through diode 26 andthrough rectifier 32 will activate the motor 34. The motor 34 will firstopen the normally closed series contacts 36 and then close the shuntcontacts 30. Thus, power supply to any more remote transmitter, such as20, is interrupted by the series contacts 36, and the diode 26 isshunted through the shunt 28. Even though the starting contact 24a isclosed in the other transmitter 20, there will be no available power foroperation.

Further rotation of the motor 34 causes the signal contacts 38 tomomentarily close, thereby activating the relay 40 in the control unitand causing reversal of polarity. The motor 34 continues to rotate inthe same direction, however, because of directed flow of current throughthe rectifier 32. Also, irrespective of the series contact 36, the othertransmitter or transmitters could not be activated because of theunidirectional conductivity thereof due to the diode 26a. Thus, thepossibility of interfering signals is eliminated until the motor 34 hasrevolved sufficiently to cause transmission of its coded signal.Thereafter, further rotation of the motor 34 causes the series contacts36 to again close, the shunt contacts to open, and the signal contacts38 to open, whereupon the relay 40 again reverses the polarity back toits initial condition after a predetermined time period of no signalsbeing received at the control unit, enabling other transmitters to sendcoded messages. If the starting contacts of several transmitters havebeen closed, the circuit will cause the signals to be transmitted in asequential order as determined by electrical distance from the controlunit.

The purpose of the diodes and power reversal relay is best illustratedwhen considering the actuation of an intervening transmitter whileanother transmitter is in operation. Assuming that the starting contact24a of the transmitter 20 is closed and is followed by closing of thecontact 24 of an intervening transmitter 18, there will be nointerference from the transmitter 18 because of its unidirectionalconductivity. In this case, it will be noted that opening of the seriescontact 360 will not isolate the intervening transmitter 18. Reversal ofpolarity, however, will prevent the intervening transmitter 18 to beenergized until the polarity is again reversed.

Although we have shown and described a preferred embodiment of theinvention, it will be obvious to those skilled in the art that variousmodifications and changes may be made to the construction and design ofthe present circuit and the parts thereof without departing from thescope and spirit of the appended claims.

We claim:

1. In a transmission system having a control unit and a plurality oftransmitters connected in parallel to a power loop from said controlunit, the improvement wherein said transmitters are normally limited tounilateral conductivity in the same direction and each has starter meansfor actuation thereof, means in each transmitter for allowing reversepolarity operation thereof in response to actuation of said startermeans,

and means for reversing the polarity of said power loop responsive toactuation of any one of said transmitters.

2. The transmission system of claim 1 wherein a signal line is providedseparate from said power loop, and normally open contacts in said signalline are associated with each transmitter, and means for closing saidcontacts in response to actuation of an associated transmitter.

A positive non-interfering transmitting circuit comprising a controlunit, a power loop from said control unit, a plurality of diodes eacharranged in parallel in said power loop, signal sending means associatedwith each of said diodes, normally open starter switch means betweeneach diode and its associated signal sending means, normally open shuntmeans around each diode and its associated switch means, a polarityreversal relay associated with said control unit and operative toreverse polarity of said power loop upon closing of any of said starterswitch means, and means for closing said shunt means in one transmitterin response to closing of associated starter switch means.

4. The circuit of claim 3 wherein said signal sending means comprises asignal line separate from said power loop, a DC motor connected betweensaid starter contacts and said loop, and normally open signal contactsassociated with each diode location between said power loop and saidsignal line, said motor being operative to open and close said signalcontacts.

5. The circuit of claim 4 wherein rectifier means is associated withsaid motor for causing the flow of current through the motor to beunidirectional irrespective of polarity reversal in said power loop.

6. The circuit of claim 4 wherein normally closed series contacts in thepower loop are associated with said motor so as to be opened thereby.

7. The circuit of claim 6 wherein said motor is operable to sequentiallyopen said series contacts, close said shunt means and close said signalcontacts.

8. A positive non-interfering transmitting circuit comprising a controlunit, a power loop from said control unit, a separate signal linecoextensive with a portion of said loop, a plurality of transmittersarranged in parallel between said loop, each station comprising a diodehaving its anode connected to the positive side of said loop, normallyopen signal contacts associated with each transmitter between saidsignal line and the negative side of said loop, normally open starterswitch means on the cathode side of said diode, normally open shuntmeans around said diode and and said starter switch means, means betweensaid starter switch means and the negative side of said loop for closingsaid shunt means and said signal contacts in response to closing of saidstarter switch means, and means for reversing the polarity of said powerloop responsive to closing of said starter switch means.

1. In a transmission system having a control unit and a plurality of transmitters connected in parallel to a power loop from said control unit, the improvement wherein said transmitters are normally limited to unilateral conductivity in the same direction and each has starter means for actuation thereof, means in each transmitter for allowing reverse polarity operation thereof in response to actuation of said starter means, and means for reversing the polarity of said power loop responsive to actuation of any one of said transmitters.
 2. The transmission system of claim 1 wherein a signal line is provided separate from said power loop, and normally open contacts in said signal line are associated with each transmitter, and means for closing said contacts in response to actuation of an associated transmitter.
 3. A positive non-interfering transmitting circuit comprising a control unit, a power loop from said control unit, a plurality of diodes each arranged in parallel in said power loop, signal sending means associated with each of said diodes, normally open starter switch means between each diode and its associated signal sending means, normally open shunt means around each diode and its associated switch means, a polarity reversal relay associated with said control unit and operative to reverse polarity of said power loop upon closing of any of said starter switch means, and means for closing said shunt means in one transmitter in response to closing of associated starter switch means.
 4. The circuit of claim 3 wherein said signal sending means comprises a signal line separate from said power loop, a DC motor connected between said starter contacts and said loop, and normally open signal contacts associated with each diode location between said power loop and said signal line, said motor being operative to open and close said signal contacts.
 5. The circuit of claim 4 wherein rectifier means is associated with said motor for causing the flow of current through the motor to Be unidirectional irrespective of polarity reversal in said power loop.
 6. The circuit of claim 4 wherein normally closed series contacts in the power loop are associated with said motor so as to be opened thereby.
 7. The circuit of claim 6 wherein said motor is operable to sequentially open said series contacts, close said shunt means and close said signal contacts.
 8. A positive non-interfering transmitting circuit comprising a control unit, a power loop from said control unit, a separate signal line coextensive with a portion of said loop, a plurality of transmitters arranged in parallel between said loop, each station comprising a diode having its anode connected to the positive side of said loop, normally open signal contacts associated with each transmitter between said signal line and the negative side of said loop, normally open starter switch means on the cathode side of said diode, normally open shunt means around said diode and and said starter switch means, means between said starter switch means and the negative side of said loop for closing said shunt means and said signal contacts in response to closing of said starter switch means, and means for reversing the polarity of said power loop responsive to closing of said starter switch means. 